Health Talk: Agnosia

Brain damage to specific parts of the brain involved with the senses can cause agnosia. Agnosia is a mental disorder characetrized by the inability to recognize certain sensory inputs, including objects, sounds, and smells. (credit: Courtesy of Wikimedia Commons)

If we see a metal fork on a table, we immediately recognize it as a fork. If we listen to our favorite song, we recognize the sounds as music. The ability to recognize environmental stimuli is something that comes naturally to us.

But some people can see the fork on the table, and knowing that it’s silvery, metal, and something we eat with, conclude it is a spoon. Or if they hear a song, they cannot understand that what they are hearing is music.

Both of these bizarre conditions can be attributed to a brain disorder called agnosia, which is a general term describing an inability to recognize anything from objects to sounds, although senses and memory are fully functional. As www.merck.com states, agnosia can be the result of brain damage or can be a birth defect. While the mechanics of perception are still unknown, the regions of the brain that are affected have been identified.

Generally, agnosia patients have damage to the temporal lobe of the brain, which is associated with sensory processing. The primary auditory complex, which is responsible for processing sounds, is located in the temporal lobe. In addition, the temporal lobe is involved in processing visual stimuli and language. Because of the versatility of the temporal lobe of the brain, damage to this region can cause many different varieties of agnosia.

According to www.psychnet-uk.com, the inability to recognize aspects of music is known as amusia; a mild and commonly known form is tone deafness, with which individuals cannot tell the difference between different pitches. With apperceptive agnosia, patients cannot recognize objects, but they can describe them accurately. This kind of agnosia can be specific to certain kinds of objects, such as things that are living. Associative agnosia is similar. Patients can categorize objects, but cannot distinguish between objects. Prosopagnosia is the inability to recognize faces — patients can no longer recognize friends or family. Other forms of agnosia have stranger symptoms. Some patients cannot distinguish between their own fingers; others can only recognize objects if they interact with them in a way other than sight, such as through touching or smelling.

According to www.ninds.nih.gov, there are no cures for agnosia, although patients can undergo therapy. For example, people with agnosia involving speech can be helped with speech therapy. However, research involving patients with agnosia can increase our knowledge of neurological pathways.Psychologists are still trying to understand the cognitive processes involved with external stimuli. By researching patients who do not have the full ability to manage their senses, we might be able to understand which parts of the brain are needed and why.